Can you show an image of your hardware setup?
Instead of using a switch you could try and only short-circuit the switch pins on the PowerBlock with, e.g., a jumper. That should turn in the Pi.
Does that change anything?
I'm pretty sure Minecraft for Pi only utilizes keyboard and mouse. This is an old version and I don't believe it's been worked on in years, it's just there for fun.
If you need help we would need the system information from this link in order to know what you are working with.
